SIM Cards or Subscriber Identity Modules are smart cards used in cellular radio telephone devices for storing subscriber information, that can readily be moved with the card from one radio telephone device to another radio telephone device, thereby enabling a user to switch the device that they use to interact with the cellular telephone network. However, just like most other areas of technology, new standards supporting increasing levels of performance are regularly being implemented and adopted. The technological area of smart cards for use as Subscriber Identity Modules is no exception.
During at least some transitions to the use of a new technology, there is a period of time during which some of the devices support only the old standard, and during which some devices might only support the new standard. An ability to support both an old outgoing standard, as well as a new incoming standard would offer a greater amount of flexibility, and ease the transition between an older standard and a new standard. Consequently during periods of transitions in technology, a degree of backwards compatibility can be beneficial.
However, supporting multiple standards simultaneously can sometimes be less than straightforward and/or can sometimes involve less than optimal design decisions or compromises than if only one of the standards needed to be supported. Other times, simultaneously supporting multiple standards can involve separate sets of circuitry including some overlap and/or duplication in circuitry that is only used with individual ones of the multiple standards as part of providing support for the multiple modes. For example, different ones of the multiple standards may use a different subset of the available interface pins, where some of the pins are used for a common purpose across two or more of the multiple standards, while other ones of the pins are separately used, and/or the manner in which they are used changes between different ones of the standards.
Furthermore some of the standards might already support different revision levels of the technology requiring some degree of flexibility as part of the configuration of the interface relative to different standards as well as between different versions of or within a particular standard. For example, some standards might support multiple signaling voltage levels and/or speeds, which need to be detected and accommodated. More specifically, some standards might initiate communications between a SIM card and its host using the higher one of two signaling voltages, and change to the lower one of the two voltages after the card identifies itself as being a particular version of one of the standards. Alternatively, a pull-up or pull-down resistor could be used on one or more of the signal lines to distinguish between two or more different versions of a particular standard, that includes different signaling speeds.
The present inventors have recognized that in accommodating multiple standards and/or multiple revisions of a particular standard, that some of the circuitry used with one of the standards can be reused with one of the other standards, and that the ability to detect the particular standard that is currently being used and automatically configuring the smart card controller and/or the smart card for use with the detected one of the multiple supported standards would similarly be beneficial.